Most yo-yos feature two disk-shaped side portions that are rigidly connected to each other, in a spaced-apart relation, by some form of axle structure. The side portions may be of a unitary or multi-part construction and are usually made out of plastic, wood and/or metal. The axle structure typically extends through the center of both side portions and can be a simple, single part structure, such as a wooden dowel, or be a more complex assembly of multiple parts. To reduce friction, many modern yo-yos employ an axle structure that includes a center-located rotatable member, such as a ball bearing unit, as the point of attachment for the yo-yo's tether.
A yo-yo tether is commonly in the form of a long string made from a plurality of cotton strands that are twisted together. To enable the securement of the tether to the axle structure, one end of the tether is usually adapted to have a loop that is positioned to encircle a center portion of the axle structure. The other end of the tether is usually tied to create a second loop that can be placed about one of a user's fingers to thereby secure the tether, and effectively the yo-yo, to the user's hand.
In a yo-yo's initial starting condition, the yo-yo's tether is wound about the axle structure and is secured to a user's finger. The user can then release/throw the yo-yo from his hand whereby the tether will rapidly unwind from about the axle structure with a concomitant rotation of the yo-yo's two side portions. When the tether fully unwinds from about the axle structure, the yo-yo may “sleep” at the end of the tether, whereby the yo-yo's side portions continue to spin without the tether rewinding on the axle structure. Once the yo-yo is sleeping, there are a number of tricks, such as “walk the dog,” that a person can perform with the spinning yo-yo. A sleeping yo-yo is also often used to perform “string tricks” that involve temporarily placing the spinning yo-yo onto a portion of the tether intermediate of the tether's two ends.
Normally, at the finish of a yo-yo trick, the user of the yo-yo will make a quick jerk on the tether to cause the yo-yo to return to the user's hand. By jerking on the tether, the user briefly tightens the tether, which is then automatically followed by a temporary slackening of the tether. In most conventional yo-yo's, once the tether goes slack, the tether's twist will cause one, or multiple, portions of the tether located proximate the axle structure to move to the side and thereby engage at least one of the yo-yo's spinning side portions. Once an engagement has occurred, the tether portion can become locked to the contacted side portion. A locking engagement is usually due to the tether becoming snagged on the side portion's surface, or to a bunching of the tether against said side portion. Once a locking engagement has occurred, further rotation of the side portion winds the tether about the axle structure, thereby causing the yo-yo to return to the user's hand.
A relatively new way to use a yo-yo is to hold the yo-yo in one hand while it is sleeping/spinning. This is enabled when the yo-yo has rotatable endcaps on each of its side portions. Such a yo-yo can be used in the conventional manner, or the user can incorporate the ability to grab the spinning yo-yo into various new yo-yo tricks.
Mushroom-shaped, acorn-shaped and propeller-shaped rotatable endcaps are known in the art. Removal of these endcaps from a yo-yo typically requires the application of outwardly-directed force on the endcap. However, prior art securement structures used with rotatable endcaps have been problematic. If the securement structure employed to hold an endcap to the yo-yo allows said endcap to be easily removed, it is not uncommon for the endcap to inadvertently disengage from the yo-yo. If instead, the securement structure securing an endcap to the yo-yo makes the endcap difficult to remove, a user will often be disinclined to remove the yo-yo's endcaps. Since there are certain tricks in which the endcaps could snag the tether, a user faced with difficulty in removing the endcaps would either not perform the tricks, or use a different yo-yo to perform the tricks. This obviously reduces the yo-yo's versatility and desirability.